JP7707713B2 - Insulated Wire - Google Patents

Description

The present invention relates to an insulated electric wire, and in particular to an insulated electric wire that has excellent flame retardancy, surface appearance, and good printability.

Conventionally, insulated electric wires are made up of a conductor and an insulating covering, and various types are known (see, for example, Patent Document 1).

Insulated wires with excellent flame retardancy have a structure in which a flame retardant is added to the resin composition of the coating material, but the amount added is so large that the flame retardant floats to the surface of the coating material, making it impossible to maintain a smooth appearance. However, the rough, rather than smooth, appearance has the advantage of creating an anchor effect and excellent printability.

On the other hand, if the amount of flame retardant added to the resin composition is reduced in consideration of the above-mentioned smoothness, the smooth appearance can be maintained, but the flame retardancy and printability are deteriorated, making it difficult to satisfy all of these characteristics.

JP 2018-113156 A

Therefore, an object of the present invention is to provide an insulated wire that is excellent in flame retardancy, surface appearance and printability.
Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

A brief overview of the representative embodiments disclosed in this application is as follows:

The insulated wire of the present invention is an electric wire having a conductor and an insulating layer covering the conductor, and the insulating layer is composed of a resin composition having (A) a polymer containing (A-1) an ethylene-based copolymer having a melt flow rate (MFR) of 2 [g/10 min] or less and (A-2) an ethylene-based copolymer having a melt flow rate (MFR) of 9 to 100 [g/10 min], and (B) a flame retardant. The (A) polymer contains 5 to 20 mass% of the (A-2) component and has an SP value of 8.73 or more, and the (B) flame retardant is contained in an amount of 60 to 100 mass parts per 100 mass parts of the (A) polymer.

The present invention provides an insulated electric wire that has excellent flame retardancy, surface appearance, and printability.

1 is a cross-sectional view of an insulated wire according to one embodiment of the present invention. FIG. 4 is a cross-sectional view of a two-core parallel electric wire according to another embodiment of the present invention.

The following describes the embodiments in detail with reference to the drawings. In all the drawings used to explain the embodiments, the same reference numerals are used for components having the same functions, and repeated explanations will be omitted. In addition, in the following embodiments, explanations of the same or similar parts will not be repeated as a general rule unless particularly necessary.

(Embodiment)
As shown in FIG. 1 , an insulated wire 10 according to this embodiment includes a conductor 1 and an insulating layer 2 that covers the conductor 1 .

The conductor 1 can be any commonly used metal wire, without any particular limitations. For example, copper wire, copper alloy wire, aluminum wire, gold wire, silver wire, etc. can be used. The conductor 1 can also be a metal wire plated with a metal such as tin or nickel around it.

The conductor 1 may also be a twisted wire made by twisting together multiple wires, or may have a structure in which multiple twisted wires are twisted together. Figure 1 shows an example of an insulated wire with a structure in which seven twisted wires are twisted together.

The insulating layer 2 is formed using a resin composition according to the present embodiment, which will be described in detail below. The thickness of the insulating layer 2 is not particularly limited, but is preferably 0.15 to 2 mm.

The resin composition for forming the insulating layer 2 of this embodiment is described in detail below. The resin composition of this embodiment contains (A) a polymer and (B) a flame retardant, and can contain additives other than the flame retardant (C) as necessary.

The polymer (A) used in this embodiment comprises (A-1) an ethylene-based copolymer having a melt flow rate (MFR) of 2 [g/10 min] or less, and (A-2) an ethylene-based copolymer having a melt flow rate (MFR) of 9 to 100 [g/10 min].

The (A) polymer is a mixed polymer containing the (A-1) component as a base polymer and containing 5 to 20% by mass of the (A-2) component. In this case, it is preferable that the (A-1) component, which is the base polymer, is contained at 70% by mass or more. By making such a mixed polymer, the characteristics of the (A-1) component, which is generally excellent in wire extrusion properties, are maintained while the highly fluid (A-2) component is blended to improve the surface appearance. In this case, if the blending amount of the (A-2) component is less than 5% by mass, the effect of improving the surface appearance is not achieved, and if it exceeds 20% by mass, the surface appearance may become rough.

Melt flow rate (MFR) is a measure of the fluidity of a resin in a solution state, and is also called melt index (MI). In this specification, melt flow rate (MFR) is a value calculated by a melt flow rate test (MFR test) in which a resin placed in a cylindrical extrusion plastometer is extruded from the bottom opening of the container under conditions of 190°C and a load of 2.16 kg in 10 minutes.

The (A) polymer is a mixture of the above-mentioned (A-1) and (A-2) components, and the SP value (solubility parameter) of the mixed polymer is set to 8.73 or more. By setting the SP value of the (A) polymer to 8.73 or more, the compatibility with printing ink is increased while the surface appearance is smooth, thereby improving printability.

The SP value (solubility parameter) is a numerical value that serves as a scale for expressing the compatibility of substances; the closer the SP values of the respective substances being mixed, the easier they will be to mix. Solvents used in printing inks are generally highly polar, and their SP values are estimated to be between 8 and 10. Therefore, printability can be improved by setting the SP value of the (A) polymer within the above range.

The SP value of the polymer (A) can be calculated according to the Fedors method using the following formula (1).
δ=[ΣE _coh /ΣV] ^1/2 ...(1)
δ: SP value [-]
E _coh : Energy of evaporation [cal/mol]
V: molar volume [cm ³ /mol]

In addition, in order to achieve flame retardancy, it is preferable that the ethylene-based copolymer blended as polymer (A) is an ethylene-ethyl acrylate copolymer (EEA) or an ethylene-vinyl acetate copolymer (EVA).

Furthermore, in order to achieve flame retardancy, it is preferable that the polymer (A) contains chlorinated polyethylene (CPE), and in this case, it is more preferable that the chlorine content in the polymer (A) is 1 to 5% by mass. If the chlorine content is less than 1% by mass, the addition of CPE will have no effect, and if it exceeds 5% by mass, there is a risk that the surface appearance of the coating material will become rough due to dehydrochlorination of the CPE during extrusion.

The CPE used here may be either amorphous or semi-crystalline CPE, and one of these CPEs may be used alone or two or more may be mixed together. In the examples described below, semi-crystalline CPE was used.

The flame retardant (B) used in this embodiment is not particularly limited as long as it is a known flame retardant that is blended into insulated electric wires, and in this embodiment, the flame retardant (B) is contained in a range of 60 to 100 parts by mass per 100 parts by mass of the polymer (A). By using such a blending method, sufficient flame retardancy can be ensured. If the content is less than 60 parts by mass, sufficient flame retardancy is not achieved, and if it exceeds 100 parts by mass, the flame retardant (B) may come to the surface of the coating material, causing the surface appearance to become rough.

Here, examples of flame retardants include halogen-based, phosphorus-based, antimony-based, and metal hydroxides, and these may be used alone or in combination of two or more. Examples of halogen-based flame retardants include bromine-based flame retardants, and examples of antimony-based flame retardants include antimony trioxide, and examples of metal hydroxide flame retardants include magnesium hydroxide, which is preferred.

From the viewpoint of obtaining good flame retardancy, it is preferable to use a mixture of two or more selected from (B-1) bromine-based flame retardant, (B-2) antimony trioxide, and (B-3) magnesium hydroxide, and it is further preferable to use a mixture of all three.

(B-1) Examples of bromine-based flame retardants include organic bromine-containing flame retardants such as brominated ethylene bisphthalimide derivatives, bisbrominated phenyl terephthalamide derivatives, brominated bisphenol derivatives, and decabromodiphenylethane. As a bromine-based flame retardant, decabromodiphenylethane is particularly preferred from the viewpoint of preventing blooming during the formation of the insulating layer.

(B-2) Antimony trioxide preferably has an average particle size of approximately 1 μm and a purity (99.5% by mass or more) of 1000 ppm or less lead content, 600 ppm or less arsenic content, 300 ppm or less iron oxide content, 200 ppm or less copper oxide content, 100 ppm or less selenium content, and 5 ppm or less cadmium content.

(B-3) Examples of magnesium hydroxide include those with untreated surfaces and those that have been surface-treated with silane coupling agents, phosphate esters, or fatty acids such as stearic acid and oleic acid.

In this embodiment, it is particularly preferable to use magnesium hydroxide that has been surface-treated with a silane coupling agent. Magnesium hydroxide that has been surface-treated with a silane coupling agent has high affinity with polymers, so that the tensile properties of the flame-retardant resin composition containing this magnesium hydroxide are excellent.

When using a mixture of two or more types of flame retardant (B) as described above, it is preferable to mix (B-1) bromine-based flame retardant at 10 to 80 mass%, (B-2) antimony trioxide at 10 to 80 mass%, and (B-3) magnesium hydroxide at 10 to 80 mass%, assuming (B) flame retardant at 100 mass%.

Additives other than the (C) flame retardant are additives that are blended into this type of resin composition and can be used without any particular limitations as long as they do not impair the effects of this embodiment. Examples include (C-1) antioxidants, (C-2) stabilizers, (C-3) copper inhibitors, (C-4) fillers, (C-5) lubricants, and (C-6) cross-linking aids.

In this embodiment, the blending amount of additives other than the flame retardant (C) is preferably 7 to 40 parts by mass, and more preferably 12 to 28 parts by mass, per 100 parts by mass of the polymer (A).

Here, examples of the (C-1) antioxidant include phenol-based antioxidants, sulfur-based antioxidants, phenol/thioester-based antioxidants, amine-based antioxidants, and phosphite-based antioxidants.

Examples of phenolic antioxidants include 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate sanstearyl, and 4,4'-butylidenebis-(6-tert-butyl-3-methylphenol).

Examples of sulfur-based antioxidants include ditetradecyl 3,3'-thiodipropionate, 2,2-bis[[3-(dodecylthio)propionic acid]-1,3-propanediyl, and dioctadecyl 3,3'-thiodipropionate.

(C-2) Stabilizers include, for example, hydrotalcite, which acts as an anion trap to capture impurities in each additive and also functions as a hydrogen chloride trap when CPE is used in the (A) polymer.

(C-3) Examples of copper damage inhibitors include hydrazides such as N'1,N'12-bis(2-hydroxybenzoyl)dodecane dihydrazide, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, and isophthalic acid bis(2-phenoxypropionylhydrazide), as well as 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzoamide and alcohol carboxylate esters.

(C-4) Examples of lubricants include zinc stearate, silicone, fatty acid amides, hydrocarbons, esters, alcohols, and metal soaps.

(C-5) Examples of cross-linking aids include trimethylolpropane trimethacrylate (TMPT), triallyl isocyanurate, triallyl cyanurate, N,N'-metaphenylene bismaleimide, ethylene glycol dimethacrylate, zinc acrylate, and zinc methacrylate.

In addition to the materials described above, fillers, pigments, etc. may be added to the resin composition of this embodiment as long as they do not affect the properties obtained in this embodiment.

<Method of manufacturing insulated wire>
The insulated wire 10 of the present embodiment shown in FIG. 1 can be produced by a known method, for example, as follows.

For example, a resin composition containing the above-mentioned resin composition constituting (A) the polymer, (B) the flame retardant, and (C) an additive other than the flame retardant, which is added as necessary, is prepared. This resin composition is compounded, and then extrusion molding is performed to cover the conductor 1. The resin is then cured by irradiating with an electron beam or the like to form the insulating layer 2, thereby obtaining the insulated electric wire 10.

More specifically, for example, (A) a polymer, (B) a flame retardant, and (C) additives other than the flame retardant are melt-kneaded in a 55 L Wonder kneader at a set temperature of 100°C and a drop temperature of 135°C. The melt-kneaded resin composition is then pelletized by strand cutting to form a compound.

Next, the compound is extruded at an extrusion outlet temperature of 150°C using a 60 mm extruder, and a separately prepared conductor 1 is coated to produce an insulated electric wire. In this coating, the extruded resin composition is irradiated with, for example, an electron beam of 6 Mrad to crosslink the compound, forming an insulating layer 2, and an insulated electric wire 10 is obtained.

When crosslinking is performed by a chemical crosslinking method, a crosslinking agent may be added to the resin composition in advance. Examples of crosslinking agents include organic peroxides such as hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, ketone peroxyesters, and ketone peroxides.

When crosslinking by silane crosslinking, a silane coupling agent is added in advance in addition to the organic peroxide. Examples of silane coupling agents include vinyl silanes such as vinyltrimethoxysilane, methacryl silanes such as 3-methacryloxypropylmethyldimethoxysilane, amino silanes such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and mercapto silanes such as 3-mercaptopropylmethyldimethoxysilane.

The above-mentioned insulated wire has been described as having one conductor 1 made of twisted wire, but it may have multiple conductors 1. For example, as shown in FIG. 2, it may be a two-core parallel wire 20 in which two conductors 1 are arranged in parallel and covered with an insulating layer 2.

The materials shown in Table 1 (the product name and manufacturer of each component are listed) were prepared as (A) polymer, (B) flame retardant, and (C) additives other than flame retardant. Table 2 shows the SP value and melt flow rate (MFR) for each component of (A) polymer shown in Table 1. In addition, in Tables 2 to 6, the EA amount indicates the proportion (mass%) of units derived from ethyl acrylate in the copolymer, the VA amount indicates the proportion (mass%) of units derived from vinyl acetate in the copolymer, and the Cl amount indicates the proportion (mass%) of chlorine in the polymer.

These materials were melt-kneaded in the formulations shown in Tables 3 to 6 in a 55L Wonder kneader with a set temperature of 100°C and a drop temperature of 135°C. The melt-kneaded resin composition was then pelletized by strand cutting to form a compound.

Next, the compound was extruded using a 60 mm extruder at an extrusion outlet temperature of 150°C, and a separately prepared conductor 1 was coated with it. The resin composition coating conductor 1 was cured by irradiating it with an electron beam of 6 Mrad to form an insulating layer, and an insulated wire was produced.

<Evaluation method>
(1) Flame Retardancy The prepared insulated wires were subjected to the vertical flame retardancy test VW-1 defined in the flame retardancy standard UL1581 10 times. Those that passed 8 times or more were evaluated as "◎", those that passed 6 to 7 times were evaluated as "◯", and those that passed 5 times or less were evaluated as "X".

(2) Printability A Teflon sheet was laid on an aluminum plate, and a 1 mm square metal frame was placed on it. The compound prepared was spread in the metal frame, and a Teflon sheet and an aluminum plate were placed on top of it. The compound was preheated at 180°C for 3 minutes, pressurized at 10 MPa for 2 minutes, and then cooled in a 70 t press to prepare a 1 mm sheet. The sheet was then irradiated with an electron beam of 6 Mrad to be crosslinked. An ink solution was applied to the crosslinked sheet, and the printability was evaluated by a cross-cut test according to JIS K 5600-5-6. The ink solution was prepared by mixing VS-09 black (manufactured by Teikoku Ink Co., Ltd.) as the base ink and E-003 (manufactured by Teikoku Ink Co., Ltd.) as the diluent at a general dilution rate of 20%.
The coating film after the test was judged as "good" if no peeling occurred, and "poor" if peeling occurred.

(3) Surface appearance The surface roughness of the prepared insulated electric wire was measured using a laser microscope. The arithmetic mean roughness Ra and maximum height Ry were measured at three random locations (n=3) and the average was calculated. Regarding the average obtained, an Ra value of less than 50 μm and an Ry value of less than 100 μm were evaluated as "good", and an Ra value of 50 μm or more or an Ry value of 100 μm or more were evaluated as "poor".

Comparative Example 1 shows that, conventionally, when EEA alone was used, a high flame retardant amount of 100 parts by mass caused problems with surface appearance, but printability and flame retardancy were good. In contrast, in Comparative Example 3, the flame retardant content was reduced to 50 parts by mass, and although the surface appearance was good, there were problems with printability and flame retardancy, and in Comparative Example 2, the flame retardant content was 60 parts by mass, and although both surface appearance and flame retardancy were achieved, there were problems with printability. This is thought to be due to a problem with compatibility with printing ink.

In Comparative Example 4, the polymer was changed to EVA to improve compatibility, and although printability improved, problems with surface appearance arose and both could not be achieved. Therefore, as shown in Examples 1 to 12, the inventors found that in order to maintain flame retardancy, the amount of flame retardant added was between 60 and 100 parts by mass, and that by including 5 to 20% by mass of a high MFR ethylene copolymer with an MFR of 9 to 100 [g/10 min] in the polymer component, extrusion flowability was improved and surface appearance of the electric wire could be achieved. In addition, by setting the SP value of the mixed polymer to 8.73 or more, compatibility with printing ink could be increased, printability could be improved, and all properties of flame retardancy, surface appearance, and printability could be made good.

Comparative examples 5 to 8 show that adding less than 5% by mass of high MFR ethylene copolymer does not produce a satisfactory effect, and adding more than 20% by mass causes the flow to become unstable and the appearance cannot be maintained.

In addition, it was found that even if the composition contains 5 to 20% by mass of a high MFR ethylene copolymer, unless the SP value of the mixed polymer is 8.73 or more, the compatibility with printing ink is poor, making it difficult to achieve both good printability and good adhesion, as compared to Comparative Examples 9 and 10.

With regard to flame retardancy, Examples 1 to 5 and 8 to 12 show that a resin composition containing CPE in the polymer component and with a chlorine content of 1 to 5 mass% in the polymer component can exhibit higher flame retardancy than conventional resins.

As described above, this embodiment provides an excellent insulated wire that has a good balance of flame retardancy, surface appearance, and printability.

The invention made by the inventors has been specifically described above based on the embodiments, but it goes without saying that the invention is not limited to the above embodiments and can be modified in various ways without departing from the gist of the invention.

1 Conductor 2 Insulating layer 10 Insulated wire

Claims (5)

An insulated wire having a conductor and an insulating layer covering the conductor,
the insulating layer is made of a resin composition having (A) a polymer including (A-1) an ethylene-based copolymer having a melt flow rate (MFR) of 2 [g/10 min] or less and (A-2) an ethylene-based copolymer having a melt flow rate (MFR) of 9 to 100 [g/10 min], and (B) a flame retardant;
the (A) polymer contains the (A-2) component in an amount of 5 to 20% by mass and has an SP value of 8.73 or more;
The (B) flame retardant includes three kinds of flame retardants, namely, (B-1) a bromine-based flame retardant, (B-2) antimony trioxide, and (B-3) magnesium hydroxide, and is contained in an amount of 60 to 100 parts by mass relative to 100 parts by mass of the (A) polymer.
1. An insulated wire comprising: The insulated wire according to claim 1,
The insulated wire, wherein the ethylene-based copolymer is an ethylene-ethyl acrylate copolymer (EEA) or an ethylene-vinyl acetate copolymer (EVA). The insulated wire according to claim 1 or 2,
An insulated wire, comprising: the polymer (A) containing chlorinated polyethylene (CPE); and a chlorine content in the polymer (A) of 1 to 5 mass %. The insulated wire according to any one of claims 1 to 3 ,
The insulated wire further comprises (C) an additive other than the flame retardant. The insulated wire according to any one of claims 1 to 4 ,
The insulated wire is a two-core parallel wire.